4,4,13,13-tetraethoxy-3,14-dioxa-8,9-dithia-4,13-disilahexadecane

Endpoint summary

Additional information

Reliable acute toxicity tests results are available for freshwater fish (Brachydanio rerio), invertebrates (Daphnia magna) and algae (Scenedesmus subspicatus). The relevant short-term values are:

Fish: LL₅₀ (96 h) >1000 mg/l, expressed in terms of the concentration of the parent substance;

Daphnia: EL₅₀ (48 h) <1 mg/l, expressed in terms of the concentration of the parent substance;

Algae: EL₅₀ (72 h) >500 mg/l; NOELR: 32 mg/l, expressed in terms of the concentration of the parent substance;

The LL₅₀, EL₅₀ and NOELR values all exceed the solubility of the substance (0.014 mg/l predicted).

One reliable toxicity to algae study is available with the read-across substance, bis[3-(triethoxysilyl)propyl]polysulfides (CAS 211519-85-6, EC 915-673-4) for freshwater algae (Desmodesmus subspicatus). The relevant values are:

Algae: EL₅₀ (72 h): 700 mg/l; EL₁₀: 60 mg/l, expressed in terms of the concentration of the parent substance.

It is likely that in the majority of studies, because of the prolonged test medium preparation phases, the test organisms were exposed to a mixture of undissolved parent substance, silanol hydrolysis product and precipitated oligomeric or cross-linked condensation products. The one exception is an one algal study in which direct addition to test medium was used (in this case, based on the static exposure regime, it is likely that the organisms would have been exposed to a mixture of the dissolved and undissolved parent substance, and then hydrolysis products towards the end of the test). Physical effects are likely to have had a role in the studies that showed effects.

The data have been obtained with test media that are likely to have contained the test substance at its solubility limit and the hydrolysis products of the substances. Nominal concentrations (saturated test media) were applied as well as WAFs were prepared. The lowest LL₅₀/EL₅₀ values that are judged not to have been influenced by the presence of undissolved material in the test media have been chosen to describe the hazard properties of the registration substance.

The hydrolysis products are freely soluble at low concentrations. It is therefore appropriate to base PNECs for the hydrolysis products on the loading rates used in the preparation of the test media. The parent substance itself appears to be non-toxic at the solubility limit.

 

Data waivers are applicable to long-term fish and invertebrate toxicity endpoints based on the absence of short-term aquatic toxicity at the limit of solubility, and the difficulty in preparing the test media in aqueous solutions.

An activated sludge respiration inhibition 3-hour EC₅₀ value of 100 mg/l (measured) was determined for the parent substance in a reliable study conducted with the read-across substance, bis[3-(triethoxysilyl)propyl]polysulfides (CAS 211519-85-6).

 

Refer to IUCLID Section 6 and Section 7.0 of the CSR for further discussion of the approach to chemical safety assessment.